Exhaust muffler and spark arrestor

ABSTRACT

A MUFFLER AND SPARK ARRESTOR FOR AN INTERNAL COMBUSTION ENGINE EXHAUST HAS AN INLET TO A DISK-LIKE HOUSING INTO WHICH THE SOUND INFLUX IS REFLECTED BY AN ANGLED WALL ONTO A SPIRAL, PERFORATED WALL BACKED BY A SOUND ABSORBING MEDIUM AND PARTLY DEFINING AN INCURLING CHAMBER BRANCHED TO PERMIT SOLIDS TO BE CENTRIFUGALLY CAST INTO A POCKET AND TO PERMIT GASES AND RESIDUAL SOUND TO ESCAPE FIRST IN AN AXIAL DIRECTION AND THEN THROUGH RADIAL DISCHARGE PASSAGES.

June 21, 1972 Filed June 18, 1971 FIG 3 P. s. MOLLER 3,672,773

EXHAUST MUFFLER AND SPARK ARRESTOR 2 Sheets-Sheet l June 27, 1972 P. s. MOLLER EXHAUST MUFFLER AND SPARK ARRESTOR 2 Sheets-Sheet 2 Filed June 18, 1971 63 FIG 4 United States Patent 3,672,773 EXHAUST MUFFLER AND SPARK ARRESTOR Paul S. Moller, Davis, Calif., assignor to Discojet Corporation Filed June 18, 1971, Ser. No. 154,385 Int. Cl. F0ln 1/10, 1/12, 3/06 U.S. Cl. 181-58 4 Claims ABSTRACT OF THE DISCLOSURE Internal combustion engines afford a repeated, pulsed exhaust at variable frequency depending upon the engine speed, the exhaust including not only the discharged gases spent by the engine but likewise acoustic waves of a widely varying frequency and intensity pattern as well as particulate matter such as glowing carbon and the like. It is increasingly necessary to control all three of these major factors. The hot or glowing particulate matter such as carbon cannot be permitted to escape, particularly if the vehicle to which the engine is applied or the engine location itself are such that the hot particles may be discharged into a combustible surrounding. The fire hazard from such particles is great.

The gaseous discharge component should be as nearly as possible released in an inoffensive direction and manner and preferably as cool as possible. The acoustic component must be attenuated as much as is feasible, consistent with little or no increase in the exhaust back pressure upon the engine, it being desirable to attetnuate those frequencies which are particularly intense or happen to be particularly annoying.

It is therefore an object of my invention to provide an exhaust mufiler and spark arrestor for use on an internal combustion engine in which all three of the mentioned components are carefully and effectively controlled.

Another object of the invention is to provide an exhaust muffler and spark arrestor that is simple in its construction and makeup so that its initial cost is relatively low and so that repairs or refurbishment can quiet easily be accomplished.

Another object of the invention is to provide a device of the character mentioned that can readily be applied to a wide range of internal combustion engines without substantial or any alteration to the exhaust pipes thereof as originally provided.

A further object of the invention is in general to provide an improved exhaust muffler and spark arrestor for use on an internal combustion engine.

Other objects together with the foregoing are attained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIG. 1 is for the most part a cross section on a vertical, longitudinal plane through the exhaust mufiler and spark arrestor as it is installed for use, the planes of section being indicated by line 11 of FIG. 4;

FIG. 2 is a detail showing in elevation, a portion of the interior construction of the device, the view being indicated by the line 2-2 in FIG. 1; 1

3,672,773 Patented June 27, 1972 FIG. 3 is an elevation of another detail of the interior construction, the view being indicated by the line 3-3 of FIG. 1;

FIG. 4 is for the most part a cross section, the plane of which is indicated by the lines 4-4 of FIG 1;

FIG. 5 is a side elevation of the structure shown in FIG. 4; and

FIG. 6 is a detail of construction, the view being indicated by the lines 6-6 of FIG. 5.

In a typical installation, the device is utilized with whatever exhaust or tailpipe 6 is ordinarily available on the engine to which the structure is applied, the tailpipe 6 being indicated by phantom lines since it is not part of the present construction. In addition, there may or may not be provided an adapter 7 designed to fit the tailpipe 6. It is illustrated since it can he included with the muffier structure which is of importance herein. The adapter 7 often is reduced somewhat in area (or diameter, since it is almost always circular) from that of the available pipe 6 in order to increase the velocity of the outfiowing material. The adapter 7, if used, is secured as by welding 8 to a muffler inlet pipe 9 of the customary sort. This fits within the adapter 7 (or the pipe 6, if no adapter is used) and is conveniently a sheet metal tube of relatively small wall thickness. A loop 11 or other means is secured thereto by Welding 12, for example, as a fastener to hold the mufiier in position on any suitable support.

The main body of the device is a disk-like housing defined in part by a circular cylindrical wall 13 concentric with a transverse axis 14 and having an opening 16 therein into which the tube 9 extends. The tube is splayed at the end and is secured as by tack Welding (not shown) to the interior of the wall 13 so that the tube 9 and the housing are united, preferably with the tube axis 17 being tangent to a circle concentric with the axis 14. Conveniently, one boundary of the tube 9 lies approximately on a diameter of the housing wall 13.

To enclose and complete the housing substantially, the Wall 13 is supplemented by a first end wall 18- which is preferably a substantially planar sheet metal disk having an upturned flange 19 defining an axial aperture 21 of a predetermined size, usually about comparable to the diameter of the inlet tube 9. While the end wall 18 can be incorporated with the circular cylindrical wall 13, it is preferred to have a separate piece and to flare the circular cylindrical wall 13. This provides a conical portion 22 over which is crimped the margin 23 of the disk 18 so that, in effect, a permanent seal is made. If the crimping is done lightly then the end wall 18 can be removed for interior access but a tighter, permanent crimp is usually preferred.

The flange 19 is secured by a light force fit or, for permanence, by tack welding or the like to a concentric, circular cylindrical tube 24, also preferably of sheet metal, and extending across the device along the axis 14. The housing is further enclosed by a second end wall 26 which, in this instance, is conveniently formed as an integral portion of the circular cylindrical wall 13. The second end wall 26 is generally planar and normal to the axis 14 and has an inturned rim 27 defining an aperture 28 concentric with the axis 14 and of substantially larger diameter than the aperture 21 so as to receive the tube 24 and still leave an annular gap 31 therebetween.

Particularly in accordance with the invention, there is likewise provided within the housing a spiral wall 33 having an initial portion 34, which is substantially planar and extends from the first end Wall 18 to the second end wall 26 and also has a tab 35 thereon which is united with the circular cylindrical wall 13 so that in effect the planar portion 34 extends substantially to the margin of the opening 16. The portion 34 can be modified to partake of a spiral curvature but for manufacturing reasons it is preferred to make this portion substantially planar or rectilinear. However, as the spiral nature of this wall is emphasized, the planar portion merges promptly with a spiral portion 37 which extends around the interior of the housing spaced a substantial and variable distance from the circular cylindrical wall 13. The portion 37 extends for approximately three-quarters of a turn of continually varying spiral configuration, the configuration being generated about the axis 14. The precise mathematical formula of the spiral configuration is of interest but need not be followed exactly within tolerances permitted of a device of this sort since manufacturing considerations also are of importance. In any event, the spiral wall is configured approximately as shown in FIG. 1.

Joined to the inner end of the spiral wall 33 and extending therefrom in a chordal direction to the outer wall 13 is a support wall 36. This is preferably joined at its inner end to the end of the spiral wall and at its outer end has a flange 37 anchored to the outer wall 13. The support wall 36 has a foot 38 secured to the second end wall 26 and likewise has a top flange 39 that is pressed tightly against the first end wall 18 upon assembly. The flange 39 deflects slightly so that a tight engagement is provided.

In accordance with the invention, it is preferred that the spiral wall 33 be made of either an appropriate metallic screen or of a perforated metallic strip, the perforations being relatively small in size but occupying about one half of the total area of the strip so that there can be flow through the strip 33 from one side thereof to the other. The space or chamber 41 defined between the two end walls, the outer Wall and the spiral wall 33 is filled with an acoustic absorbent material 42, for example, glass fiber, asbestos or the like.

Also provided within the housing and in special relationship to the spiral wall 33 is a deflector wall 43 having a planar initial portion 44. The wall 43 extends to both the end walls 18 and 26 and is fastened in place by a tab 45 secured to the wall 13 adjacent the margin of the opening 16. Merging with the planar portion 44 is a spiral portion 46 having a foot flange 47 secured to the adjacent end wall and terminating approximately on a diameter of the housing after extending for about onethird of a turn.

Also disposed in the housing is a baffle Wall 48 extending to the end walls and of a spiral configuration. The baffle wall merges with the wall 43 at one end and at the other end has a bent cusp 49 spaced from the end of the spiral wall 33 to leave a gap 51.

The cusp 49 is also at the end of a guide wall 56 extending to the deflector wall 43 and spanning the space between the two end walls. The wall 56 and the support wall 36 together with the circular cylinder wall 13 and the end walls define a receptacle 57 to which access from the outside may be had through a removable plug 58.

While the structure will operate as so far described, it is preferred to afford an additional member. As particularly shown in FIGS. 4 and 5, the tube 24, after passing through the aperture 28 is somewhat flared and is fastened to an inwardly flared neck 61 on an outlet plate 62 that is substantially planar and concentric with the axis 14. The main body of the outlet plate is spaced from but is fastened to the end wall 26. Parts of the outlet plate are additionally formed to provide a number of support ribs 63. These are fastened to the wall 26 and leave intervening spaces open to the annular passage 31 and terminating at the periphery of the outlet plate 62. Any convenient number of support ribs 63 can be provided. In the present instance, six are deemed adequate and they are preferably made with their length or axes each substantially tangent to the wall of the tube 24.

In the operation of this structure, the efflux from the exhaust pipe 6, accelerated by passage through the adapter 7, if used, is received in the inlet 9 and flows generally along the axis 27. As an example, aparticular sound wave, represented by a broken line 66, enters in an axial direction and impinges against the deflector wall 43, particularly in the planar portion thereof. The wall 43 is particularly positioned or angled so that it acts as a reflector particularly for waves that follow the optical rule that the angle of reflection is equal to the angle of incidence. The Wall 43 particularly does not substantially reflect back into the inlet pipe 9 but rather into the housing. Since the sound waves of many of the frequencies considered herein follow optical laws in many respects, the representative incident wave 66 entering along the path 66 is reflected at a comparable angle and, as shown by the dotted line 66, bounces back and forth in a zigzag pattern between the walls 43 and 33, the angles varying from place to place and the path of reflectance varying in length from place to place.

The wall 33 being perforate, some of the sound wave at each incidence against the wall 33 passes through perforations or reticulations in the wall and is multiply reflected at random within the sound absorption material 42 within which some of its energy is converted to heat and, therefore, is no longer acoustical. As shown by the continuation of the dotted line 66, whatever sound wave energy remains ultimately flows through the annular opening 31 and to the atmosphere through the multiple outlets between the ribs 63, being by this final, scattered or distributed dissipation substantially reduced in energy and audible effect.

Incoming gas usually follows a path determined by turbulent flow in the channel defined between the walls 33 and 43 and their successors so that the gas tends to flow as indicated by arrows 67 until most of the gases arrive at the cusp 49. Since the chamber 57 is closed and has no outlet, gas does not flow through the gap 51 but rather follows further around inside the bafile wall 48 and eventually flows over the tube 24 out the outlet opening 31 and through the discharge passages between the ribs 63 to the atmosphere. The gas is released in a sort of disk-like pattern and in varying directions.

The final principal ingredient of the exhaust; that is, carbon or comparable hot or glowing particles having substantial mass tend to be thrown by centrifugal force toward the outside wall 33 of the spiral passage and to flow along the interior of the wall 33 until they arrive at the vicinity of the cusp 49. Since in that zone the relatively massive particles have a substantial centrifugal or radially outward component, they do not follow the arrows 67 but rather are thrown outwardly through the gap 51 being then deflected by the wall 56 to fall into the receptacle 57 and lodge quietly near the bottom thereof in a position to be removed whenever the outlet plug 58 is removed.

In accordance with this arrangement, therefore, the sound component of the exhaust is multiply reflected away from the inlet pipe and has much of its energy converted to heat by traveling into a mass of absorbent material such as fiber glass, the gas itself follows a generally favorable, inwardly spiraling path to be released through a number of substantially radial outlets, there being a great deal of metal surface for the gases to impinge against so that they dissipate their heat to the atmosphere through a large amount of surface; and the final component, the solid particles of the exhaust and which may be potentially dangerous as sparks, are carried around centrifugally and are separated and thrown into a sequestered chamber for ultimate and safe removal.

Actual operation of a device constructed as shown herein has demonstrated that the audible portion of the exhaust stream has been reduced to non-annoying and acceptable levels even in quiet surroundings, that the solid particles of sizes sufficient to be a fire hazard if discharged are segregated and trapped and are not discharged and that the gas component travels through the device under improved conditions so that a monometer reading indicates a substantial reduction in back pressure in the engine exhaust in contrast to the pressure existing when the device is not used.

What is claimed is:

1. An exhaust mufllier and spark arrestor for use on an internal combustion engine exhaust pipe comprising a housing having a circular cylindrical wall having a central axis and having an opening, an inlet pipe having an axis and joined to said housing around the margin of said opening, a first end wall normal to said axis and engaging said circular cylindrical wall, said first end wall having an axial aperture of predetermined size therein, a second end wall normal to said axis and engaging said circular cylindrical wall, said second end wall having an aperture of greater than predetermined size therein, a tube arranged coaxially within said housing and at one end in engagement with said first wall at the margin of said aperture therein and at the other end passing through said aperture in said second wall spaced from the margin of said aperture therein, a spiral wall within said housing centered on said axis and extending substantially to said first wall and to said second wall, said spiral wall at one end terminating at said circular cylindrical wall adjacent the margin of said opening therein and at the other end terminating after approximately three-quarters of a turn, said spiral being spaced from said circular cylindrical wall, a support wall extending substantially to said first wall and to said second wall and from said other end of said spiral wall to said circular cylindrical wall, a deflector wall extending substantially tosaid first wall and to said second wall and at one end terminating at said circular cylindrical wall adjacent the margin of said opening and having a planar portion extending from said margin substantially across said opening at an angle to the axis thereof eflective to reflect materials and energy entering said housing through said inlet pipe and said opening onto said spiral wall and having a curved portion extending from the end of said planar portion through substantially one-quarter turn, and a baffie wall extending substantially to said first wall and to said second wall and having a spiral portion extending from a location radially inward from the end of said spiral wall and leaving a gap therebetween to the junction of said planar portion and said curved portion.

2. A device as in claim 1 including an outlet plate normal to and having portions spaced from said second end plate and engaging the other end of said tube.

3. A device as in claim 1 in which said spiral wall is perforate and including acoustic absorption material in the space between said spiral wall and said circular cylindrical wall.

4. A device as in claim 1 including an outlet plug in said housing between said support wall and said deflector wall.

References Cited UNITED STATES PATENTS 2,171,341 8/1939 McMahan 181-58 UX 2,670,055 2/1954 Dorman et a1. 181-58 UX 2,705,546 4/ 1955 Chafiey 181-35 A FOREIGN PATENTS 1,121,745 5/1956 France 181-35 A 1,163,444 4/1958 France 181-50 1,207,490 9/1959 France 1551-35 A ROBERT S. WARD, JR., Primary Examiner US. Cl. X.R.

181-35 A, 36 R, 33 E, 50, 72 

